Multi-stage hydraulic fracturing tool and system with releasable engagement

ABSTRACT

The invention relates to a multi-stage hydraulic fracturing tool and system for controllably exposing selected locations along a wellbore to a pressurized fluid. The system includes a casing having one or more ports, one or more actuation members which travel down a borehole, and one or more sliding sleeves which initially cover some of the ports and are movable using a mating actuation member to uncover those ports. The system further includes a stop mechanism to contact the sliding sleeve member after the sliding sleeve member has moved a first distance downhole under a first predefined amount of force, and a release mechanism to cause the actuation member to disengage from the sliding sleeve member release under a second predetermined amount of force.

CROSS REFERENCE TO RELATED APPLICATION

This document claims the benefit under 35 U.S.C. § 119 of U.S.Provisional Patent Application No. 62/718,757, filed Aug. 14, 2018,which is hereby incorporated by reference in its entirety.

FIELD

The present invention pertains to the field of hydraulic fracturing ingeneral and in particular to multi-stage hydraulic fracturing involvingcontrolled exposure of selected locations along a wellbore to createmultiple fracture treatments from a wellbore.

BACKGROUND

Hydraulic fracturing (“fracking”) and multi-stage hydraulic fracturingare methods used to increase the economic viability of the production ofoil and gas wells. Hydraulic fracturing to extract oil and natural gasinvolves injecting pressurized fluid and proppant through the wellboredown to and into the reservoir that contains the hydrocarbons, in orderto propagate fissures in the rock layers. By this process the fissuresare filled with proppant, and become the paths by which the oil and gasflow out of the rock layers and into the wellbore system. Severalmethods of hydraulic fracturing have been utilized.

Multi-stage hydraulic fracturing methods typically require the use ofmultiple isolation members installed sequentially in the wellbore thatallow for sequential isolation and treatment of intervals of thewellbore. Usually, the sequential isolation and fracturing of thewellbore is completed from the lower end to the upper end as this istraditionally considered to be the most operationally efficient and thelowest risk approach. Isolation members have included wireline setplugs, graduated balls, balls in a ‘counting’ or ‘ratcheting’ stylesystems, plugs that have geometric profiles on them that only willengage a unique location in the wellbore, coiled tubing run packers aswell as others. Often sliding sleeves will also be employed togetherwith the sequentially installed isolation members so that a slidingsleeve can be shifted into an open position which exposes ports throughthe casing to the reservoir which may be used as a conduit to place afracture treatment into the reservoir from surface pumps.

The graduated ball activated sliding sleeve style of system as disclosedin U.S. Pat. No. 6,907,936 uses balls pumped from the surface as theisolation members. This method involves the sliding sleeve ball dropmethod which uses a graduated ball size functionality. This processinvolves first installing a production casing or liner having ports,which are covered with sliding sleeves. Each sleeve has a ball seat of adifferent and gradually larger diameter. To pump a fracture treatment, aball is dropped into the wellbore and is pumped down to itscorresponding size of ball seat where it lands and forms at least apartial seal. Pressure is increased in the upper portion of the wellboreabove the seated ball until a shear member in the sleeve shears due tothe pressure differential, causing the now free sliding sleeve to movedeeper into the wellbore and exposing a now opened port between thewellbore and the reservoir. In this method, the ball and ball seat arethe isolation member. The fracture treatment is then pumped through thatport until completed, and the next larger ball is then dropped whichwill land and seal at the next shallowest stage. The process is repeateduntil all desired stages have been opened and fracked. Each fracturingstage is isolated from the one below it with a slightly larger ball. Thesystem has a finite number of stages because the size of the ballseventually increases to a size that is too large to be pumped down thewellbore. The major drawback to this method is that the number of stagesis limited by the diameter of the casing, which limits the number ofballs used, and in turn the number of stages that can be fractured.Another drawback is that the ball seats are restrictions in the wellborethat will restrict well production or need to be milled out with coiledtubing increasing well costs.

Coiled tubing activated sliding sleeves use a packer and slips on thebottom hole assembly of coiled tubing to seal and engage on a slidingsleeve. The well is then pressured up which transmits a hydraulic forceto the sliding sleeve shearing it open and exposing ports that afracture placement may be pumped through. In this method the seals andslips on the bottom hole assembly act as the isolation member. Thelimitation of the method is that coiled tubing is required adding extracosts. Also, because coiled tubing is required, the lateral length thatsleeves can be actuated is limited to as far as coiled tubing can reach.Coiled tubing cannot reach the same lateral lengths of casing as casingcan be buoyed and or rotated to bottom increasing reach. The benefit ofthis type of method is that a substantially unlimited number ofintervals may be fractured. Another benefit is that if a screenout isexperienced during fracturing it can easily be cleared via circulationand the next uphole stage can be easily opened to regain connectivity tothe reservoir.

Plug activated sliding sleeve systems, in which the plug and plug sealis the isolation member, involve first installing a casing or linerhaving ports which are covered with sliding sleeves. Each sliding sleevehas a particular profile which allows it to selectively engage withplugs having corresponding “matching” profiles. To pump a fracturetreatment, a plug is dropped into the wellbore and is pumped down to itscorresponding sliding sleeve where it mates, engages and at leastpartially forms a seal. Pressure is increased in the upper portion ofthe wellbore above the engaged plug until a shear member in the sleeveshears due to pressure differential. This causes the now free slidingsleeve to move deeper into the wellbore and exposes a now-opened portbetween the wellbore and the reservoir. The fracture treatment is thenpumped through that port until completed. After this, another plug ispumped down the well which mates with the sliding sleeve at the nextshallowest stage. The process is repeated until all desired stages havebeen opened and fractured. Each fracturing stage is isolated from theone below it with sequentially landed plug. This type of system mayaccommodate a greater number of stages than ball drop systems becausethere is significantly more freedom in creating different plug andsliding sleeve member profiles than there is in creating different balldiameters. As an example, 300 single point of entry fracture intervalscan be obtained with this style of system.

A limitation with existing plug activated sliding sleeve systems is thatthe plug, once mated to the sliding sleeve, becomes a restriction in thewellbore. The plugs generally cannot be milled out economically becausethey are made from high strength steel. It is also not economical toretrieve them with coiled tubing or wireline because of the large numberof runs in and out of the hole that would be required, as well as thehorizontal reach limitations of coiled tubing and wireline. Theserestrictions lower well production when compared to a full bore well andcan inhibit a full range of remedial wellbore operations such asrefracturing. These systems also do not allow for immediate remediationof screenout events. If a screenout occurs and cannot be cleared byflowback, then coiled tubing must be run into the well to clear thescreenout. Alternatively, perforating above the screened-out intervalmay be required to regain injectivity to the reservoir so that plugs canbe pumped down. Another potential drawback with these systems is thatthey typically require a dissolving material to be present in the boreof the plug. Such materials can be costly to produce, representing asignificant portion of the cost of the systems.

Therefore, there is a need for a system for multistage hydraulicfracturing that is not subject to one or more limitations of the priorart.

This background information is provided to reveal information believedby the applicant to be of possible relevance to the present invention.No admission is necessarily intended, nor should be construed, that anyof the preceding information constitutes prior art against the presentinvention.

SUMMARY

In accordance with an aspect of the invention, there is provided amulti-stage hydraulic fracturing tool and system. In accordance with anembodiment of the present invention, there is provided a system forcontrollably exposing selected locations along a wellbore to apressurized fluid, the wellbore including an elongated casing disposedtherein, the casing defining an internal borehole extendinglongitudinally with the wellbore, the casing having one or more portsextending through the casing. The system comprises an actuation memberconfigured for travelling down the borehole in a longitudinal direction;a first sliding sleeve member for disposal within the borehole andhaving an aperture for receiving the actuation member therein. The firstsliding sleeve member is configured to initially cover one of the one ormore ports, and further configured to move downhole in response to apredetermined amount of force in the longitudinal direction to uncoverthe port. The actuation member comprises a first engagement portionconfigured to matingly engage with a corresponding second engagementportion of the sliding sleeve member to allow for the predeterminedamount of force to be transferred from the actuation member to thesleeve member. A stopping member is affixed to the casing downhole ofthe sliding sleeve member. The stopping member is configured to contactthe sliding sleeve member after the sliding sleeve member has moved afirst distance downhole and initially inhibit further downhole travel ofthe sliding sleeve member. The stopping member is further configured torelease under a second predetermined/defined amount of force to allowthe further downhole travel of the sliding sleeve member. The firstengagement portion and the second engagement portion are configured torelease from one another upon the further downhole travel of the slidingsleeve member under the second predetermined amount of force, to causethe actuation member to disengage from the sliding sleeve member.

In accordance with another embodiment of the present invention, there isprovided a system for controllably exposing selected locations along awellbore to a pressurized fluid, the wellbore including an elongatedcasing disposed therein. The casing defining an internal boreholeextending longitudinally with the wellbore, and the casing having one ormore ports extending through the casing. The system comprises anactuation member configured for travelling down the borehole in alongitudinal direction and at least one sliding sleeve member fordisposal within the borehole and each having an aperture for receivingthe actuation member therein. The at least one sliding sleeve memberconfigured to initially cover a respective port, and further configuredto move downhole in response to a predetermined amount of force in thelongitudinal direction to uncover the port. The actuation membercomprises a first engagement portion configured to matingly engage witha corresponding second engagement portion of the at least one slidingsleeve member to allow for the predetermined amount of force to betransferred from the actuation member to the sleeve member. A stoppingmember is affixed to the casing downhole of more or more of the at leastone sliding sleeve member, the stopping member is configured to contactthe sliding sleeve member after the sliding sleeve member has moved afirst distance downhole and initially inhibit further downhole travel ofthe sliding sleeve member. The stopping member is also configured torelease under a second predetermined amount of force to allow thefurther downhole travel of the sliding sleeve member. The firstengagement portion and the second engagement portion are configured torelease from one another upon the further downhole travel of the slidingsleeve member under the second predetermined amount of force, to causethe actuation member to disengage from the sliding sleeve member.

BRIEF DESCRIPTION OF THE FIGURES

Further features and advantages will become apparent from the followingdetailed description, taken in combination with the appended drawing, inwhich:

FIG. 1 illustrates, in a sectional view, a system in accordance with anembodiment of the present invention in a wellbore;

FIG. 2A illustrates, in a cross sectional view, an actuation member inaccordance with an embodiment of the present invention;

FIG. 2B illustrates, in a cross sectional view, an actuation member inaccordance with another embodiment of the present invention;

FIG. 2C illustrates, in a cross sectional view, an actuation member inaccordance with another embodiment of the present invention;

FIG. 3 illustrates, in a cross sectional view, a sliding sleeve memberin accordance with an embodiment of the present invention in a casing,for interoperation with the actuation member of FIG. 2A, 2B or 2C;

FIGS. 4A to 4B illustrate, in sectional views, operation of an actuationmember with respect to the casing having a release mechanism inaccordance with an embodiment of the present invention.

FIGS. 5A to 5J illustrate, in sectional views, operation of an actuationmember with respect to the casing having a stopping member and a releasemechanism in accordance with another embodiment of the presentinvention.

FIGS. 6A to 6I illustrate, in sectional views, operation of an actuationmember with respect to the casing having a stopping member and a releasemechanism in accordance with another embodiment of the presentinvention.

FIGS. 7A to 7H illustrate, in sectional views, operation of an actuationmember with respect to the casing, in accordance with another embodimentof the present invention.

FIGS. 8A to 8I illustrate, in sectional views, operation of an actuationmember having an optional stopping member, with respect to the casing,in accordance with another embodiment of the present invention.

FIGS. 9A to 9C illustrate, in sectional views, operation of an actuationmember having an optional stopping member, with respect to the casing,in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention provide a system for controllablyexposing selected locations along a wellbore to a pressurized fluid,wherein the wellbore includes an elongated casing disposed therein,which defines an internal borehole extending longitudinally with thewellbore, and the casing has one or more ports extending through thecasing. The system includes a casing having one or more ports, one ormore actuation members which travel down a borehole, and one or moresliding sleeves which initially cover some of the ports and are movableusing a mating actuation member to uncover those ports. The systemfurther comprises a release mechanism and a stopping mechanism downholeof the sliding sleeve member. The stopping mechanism is configured tocontact the sliding sleeve member after the sliding sleeve member hasmoved a first distance downhole under a first predetermined/predefinedamount of force (e.g. due to hydraulic pressure) and initially inhibitfurther downhole travel of the sliding sleeve member. The stoppingmember is further configured to release (e.g. by breaking) under asecond predetermined amount of force to allow the further downholetravel of the sliding sleeve member, and interact with the releasemechanism to cause the actuation member to disengage from the slidingsleeve member.

In accordance with an embodiment, there is provided a system comprisingcasing having one or more ports, one or more actuation members whichtravel down a borehole, and one or more sliding sleeves which initiallycover some of the ports (e.g. using shear pins) and are movable using amating actuation member to uncover those ports. The one or more sleevesare configured to move downhole in response to apredetermined/predefined amount of force in the longitudinal directionto uncover the port. The actuation member comprises a first engagementportion configured to matingly engage with a corresponding secondengagement portion of the sliding sleeve member to allow for thepredetermined amount of force to be transferred from the actuationmember to the sleeve member.

Further provided is a stopping member affixed to the casing downhole ofthe sliding sleeve member, the stopping member configured to contact thesliding sleeve member after the sliding sleeve member has moved a firstdistance downhole and initially inhibit further downhole travel of thesliding sleeve member. The stopping member is configured to releaseunder a second predetermined/predefined amount of force to allow thefurther downhole travel of the sliding sleeve member. The firstengagement portion and the second engagement portion are furtherconfigured to release from one another upon the further downhole travelof the sliding sleeve member under the second predetermined amount offorce, to cause the actuation member to disengage from the slidingsleeve member.

Once disengaged, an actuation member can be pumped further down theborehole.

Actuation members may also be referred to herein as plugs in the sensethat they plug the borehole when engaged with a sliding sleeve.Embodiments of the present invention can be configured to releaseactuation members from sleeves.

In some embodiments, the first engagement portion of the actuationmember comprises a wedged portion and a groove formed at least partiallycircumferentially around an outer surface of the actuation member, andthe first engagement portion of the sliding sleeve comprises one or moreinward-facing protrusions connected to the sliding sleeve member, andprotruding radially into the aperture. One or both of the protrusionsand the groove are configured, upon alignment of the protrusions and thegroove, to move radially toward the other due to a biasing force so thatthe protrusions are received within the groove, whereupon thepredetermined amount of force is transferred from the actuation memberto the sleeve member.

In some embodiments, the groove can be instead formed on the slidingsleeve member and the mating protrusion can be formed on the actuationmember. A variety of such releasable mating mechanisms can be provided.

In the embodiments involving the above-mentioned wedged portion, whenthe wedged portion is subjected to a force oriented opposite to thedownhole direction (in which the actuation member is tending to travel),this force tends to push the part of the actuation member having thegrooves (or protrusions) radially inward due to a levering action. Thislevering action can be used to facilitate the mating of actuation memberand sliding sleeve member. Furthermore, this levering action can be usedto facilitate the subsequent release of the actuation member from thesliding sleeve member.

In some embodiments, the wedged portion is located along a leading edgeof the actuation member.

In some embodiments, the wedged portion protrudes from the outer surfaceof the actuation member at a location between a leading edge and atrailing edge of the actuation member.

In some embodiments, one or both of the actuation member and the slidingsleeve member have a resilient deformation region.

In some embodiments, the actuation member itself can be resilientlydeformable in the radial inward direction. A portion of the actuationmember which is resiliently deformable may also be referred to as a(resilient) deformation region.

In some embodiments, the actuation member has a deformation regioncomprising the groove disposed thereon; wherein the biasing force isgenerated by resilient radial inward deformation of the deformationregion, the resilient radial inward deformation occurs in response toaction of the wedged portion on the protrusions during downhole motionof the actuation member past the protrusions.

In some embodiments, the deformation region of the actuation member isthe trailing portion of the actuation member. The deformation region ofthe actuation member may be colleted and includes the actuation membergroove. Longitudinal cuts (collets) can be formed within a resilientmaterial forming the (hollow) actuation member in order to allow theactuation member to be radially inwardly compressible in response toforce imparted on the wedged portion by the protrusions (of the slidingsleeve member) when the actuation member moves downhole past theprotrusions. It is noted that a variety of design options are availablein which: a portion of the sliding sleeve member radially outwardlydeforms while the actuation member remains undeformed; the actuationmember radially inwardly deforms while the sliding sleeve member remainsundeformed; or both the portion of the sliding sleeve member radiallyoutwardly deforms and the actuation member radially inwardly deforms.

In some embodiments, downhole of the stopping member, the borehole orcasing has a narrowing portion configured to contact and apply force onthe wedged portion of the actuation member due to the further downholetravel. This force causes a second instance of radial inward deformationof the deformation region to release the protrusions from the groove, tocause the actuation member to disengage from the sliding sleeve member,thereby providing a release mechanism.

In some embodiments, downhole of the stopping member the casingcomprises a protruding body configured to contact to and apply force onthe wedged portion of the actuation member due to the further downholetravel. This force causes a second instance of radial inward deformationof the deformation region to release the protrusions from the groove, tocause the actuation member to disengage from the sliding sleeve member,thereby providing a release mechanism. In some embodiments, theprotruding body is wedge shaped.

In some embodiments, the release mechanism comprises a wedge-shaped bodyconfigured to contact a wedged portion of an actuation member havinggrooves, and radially inwardly deform the wedged portion and a trailingportion as the actuation member moves downhole, the groove mounted onthe trailing portion, thereby disengaging the groove from theprotrusions of the sliding sleeve member.

In some embodiments, the system further comprises a second slidingsleeve member for disposal within the borehole uphole of the firstsliding sleeve member. The second sliding sleeve member has a secondaperture for receiving the actuation member therein. The second slidingsleeve member initially covers a second port of the one or more portsextending through the casing and configured, upon application of asecond predetermined amount of force applied in the longitudinaldirection, to move downhole in the longitudinal direction, therebyuncovering the second port. A second stopping member affixed to thecasing downhole of the second sliding sleeve member. The second stoppingmember is configured to contact the second sliding sleeve member afterthe sliding sleeve member has moved a first distance downhole andinitially inhibit further downhole travel of the second sliding sleevemember. The second stopping member is further configured to releaseunder another predetermined/predefined amount of force to allow thefurther downhole travel of the sliding sleeve member. The second slidingsleeve member comprises an engagement portion configured to matinglyengage the first engagement portion of the actuation member, to allowfor the predetermined amount of force to be transferred from theactuation member to the sleeve member. The first engagement portion andthe engagement portion of the second sleeve are configured to releasefrom one another upon the further downhole travel of the sliding sleevemember under the second predetermined amount of force, to cause theactuation member to disengage from the sliding sleeve member.

The system further comprises one or more second inward-facingprotrusions connected to the second sliding sleeve member, wherein thesecond protrusions at least initially protrude radially into the secondaperture, wherein the second protrusions has a second further length inthe longitudinal direction, and the second further length is less thanor equal to the further length. One or both of the second protrusionsand the second groove is configured, upon alignment of the secondprotrusions and the second groove, to move radially toward the other dueto a biasing force so that the second protrusions are received withinthe second groove, whereupon the predetermined amount of force istransferred from the second actuation member to the second sleevemember. The one or both of the second actuation member and the secondsliding sleeve have a second deformation region, wherein the seconddeformation region of the second sliding sleeve has the one or moreinward facing protrusions, wherein the biasing force is generated by oneor both of: resilient radial outward deformation of the seconddeformation region of the second sliding sleeve member, and resilientradial inward deformation of the second actuation member, the resilientradial outward and inward deformation occurring in response to action ofthe second wedged portion on the second protrusions during downholemotion of the second actuation member past the second protrusions.

In some embodiments, the actuation member initially is configured tosubstantially fill the borehole and travels down the borehole inresponse to hydraulic pressure applied uphole of the actuation member.

In some embodiments, actuation member includes a longitudinal apertureextending from an uphole face of the actuation member to a downhole faceof the actuation member, and a plug member seat within the longitudinalaperture, the plug member seat configured for receiving and retaining aplug member for blocking the longitudinal aperture. In some embodiments,the plug member is controllably dissolvable.

In some embodiments, the actuation member includes a leading portion anda trailing portion, wherein the leading portion located downhole of thetrailing portion. The trailing portion is compressible radially inwardlydue to force applied by the one or more inward-facing protrusions on thewedged portion when the actuation member moves downhole past the one ormore inward-facing protrusions of a sleeve.

In some embodiments, the trailing portion comprises resilientlydeformable collets actuated for radially inward compression.

In some embodiments, the actuation member includes a longitudinalaperture extending from an uphole face of the actuation member to adownhole face of the actuation member, and wherein the leading portioncomprises a plug member seat within the longitudinal aperture, the plugmember seat configured for receiving and retaining a plug member forblocking the longitudinal aperture and receiving a downhole hydraulicforce for propelling the actuation member.

In another aspect, the system of the present invention comprises anactuation member configured for travelling down the borehole in alongitudinal direction; one or more sliding sleeve members for disposalwithin the borehole, and each having an aperture for receiving theactuation member therein. The one or more sliding sleeve members areconfigured to initially cover a respective port, and further configuredto move downhole in response to a predetermined amount of force in thelongitudinal direction to uncover the port. The actuation membercomprises a first engagement portion configured to matingly engage witha corresponding second engagement portion of the one or more slidingsleeve members to allow for the predetermined/predefined amount of forceto be transferred from the actuation member to the sleeve member. Thesystem is further provided with a stopping member affixed to the casingdownhole of one or more of the at least one sliding sleeve member. Thestopping member is configured to contact the sliding sleeve member afterthe sliding sleeve member has moved a first distance downhole andinitially inhibit further downhole travel of the sliding sleeve member.The stopping member is further configured to release under a secondpredetermined amount of force to allow the further downhole travel ofthe sliding sleeve member. The first engagement portion and the secondengagement portion are configured to release from one another upon thefurther downhole travel of the sliding sleeve member under the secondpredetermined amount of force, to cause the actuation member todisengage from the sliding sleeve member.

In some embodiments, the stopping member is affixed to the casingdownhole of each of the at least one sliding sleeve member.

In some embodiments, the system further comprises at least oneadditional actuation member, wherein the at least one additionalactuation member comprises a first engagement portion configured tomatingly engage with a corresponding second engagement portion of the atleast one sliding sleeve member, which is different than the slidingsleeve member engaged with the first actuation member. Thisconfiguration can be achieve by providing different mating structuresand/or by difference in outer diameter of the additional actuationmembers as discussed elsewhere herein.

In some embodiments, the stopping members and release mechanisms areincluded with only some of the sliding sleeve members.

The combination of the stopping member, and the releasable matingmechanism operates as follows. Following engagement of the actuationmember and the sliding sleeve member, the sliding sleeve member ispushed downhole until it abuts a frangible stopping mechanism (stoppingmember), such as a shear pin or shear ring. The stopping mechanism isbreakable under a predetermined amount of force in the downholedirection, this force being greater than the amount of force due tohydraulic pressure applied when initially moving the sliding sleevemember to uncover the port. When release of the actuation member isdesired, this amount of force can be applied by increased hydraulicpressure, optionally following a blocking of the port (and other upholeports). This hydraulic pressure presses on the actuation member, whichin turn presses on the sliding sleeve member, which further in turnpresses on the stopping mechanism, causing it to break or release. Thesliding sleeve member and actuation member then travel further downholea limited distance, until the actuation member's wedged portionencounters a radially inwardly (possibly angled) protruding body affixedto the borehole perimeter. This encounter causes the levering action asdiscussed above, which disengages the actuation member's groove (orprotrusions) from the sliding sleeve member's protrusions (or groove).This causes the actuation member to release from the sliding sleevemember so that it can continue to be pushed downhole away from thesliding sleeve member.

Increasing hydraulic pressure can be assisted by re-blocking the ports,either with balls, or an intentional or unintentional screenout event,or a port not accepting fluid for whatever reason.

The stopping member can comprise a shear mechanism, such as a shear pin,a plurality of shear pins, or a shear ring, configured to break under apredetermined pressure.

The inclusion of a release mechanism allows a single actuation member toengage with and move multiple sliding sleeve members. As explainedelsewhere herein, the actuation member only engages with and movessliding sleeve members which have protrusions of the appropriatedimensions (e.g. length) to fit within the actuation member's groove.However, multiple such sliding sleeve members can be included within theborehole and the actuation member can sequentially engage with andactuate each sliding sleeve member as the actuation member movesdownhole. Each of these multiple sliding sleeve members, exceptoptionally the sliding sleeve member furthest downhole, is associatedwith a release mechanism.

In some embodiments, the actuation member is configured to selectivelyengage with the sliding sleeve member and one or more first furthersliding sleeve members disposed within the borehole, and to pass withoutengagement through one or more second further sliding sleeve members,disposed within the borehole. The first further sliding sleeve membersand the second sliding sleeve members are configured to initially coverrespective ones of the ports and move downhole to uncover the respectiveones of the ports.

In some embodiments, the system further comprises a second actuationmember configured for travelling down the borehole in the longitudinaldirection, wherein the second actuation member includes a second wedgedportion and a second groove formed at least partially circumferentiallyaround an outer surface of the second actuation member. The secondgroove has a further length in the longitudinal direction, wherein thesecond actuation member has an outer diameter that is smaller, by apredetermined factor, than a diameter of the aperture of the slidingsleeve member. The predetermined factor is sufficiently large to inhibitthe protrusions from being retained within the second groove duringdownhole motion of the second actuation member past the sliding sleevemember.

In some embodiments, an anti-rotation mechanism, such as apin-and-groove mechanism, is provided between the sliding sleeve memberand the casing. The anti-rotation mechanism inhibits rotation of thesliding sleeve member. This may be useful for example when the slidingsleeve member or aperture thereof is being milled out.

In some embodiments, a C-ring or other one-way-motion or lockingmechanism is provided with the sliding sleeve member and configured toretain the sliding sleeve member in the downhole (open) position oncethe sliding sleeve member has been moved so as to uncover the ports.

Embodiments of the present invention can utilize two or more families oftools in the same wellbore. A tool refers to a sliding sleeve member oractuation member, and a family of tools refers to a set of actuationmembers and sliding sleeve members, such that the actuation members arecapable of engaging with and moving the sliding sleeve members, providedthat the grooves and protrusions are of mating size. For furtherclarity, even if the protrusions and grooves of a sliding sleeve memberand an actuation member, respectively, are mismatched such thatengagement is inhibited, the sliding sleeve member and actuation memberare still considered part of the same family if this is the only featureinhibiting the engagement.

As an example, a first family of tools can include sliding sleevemembers whose aperture is of a first diameter, and actuation memberssized to approximately the same first diameter, while a second family oftools can include sliding sleeve members whose aperture is of a seconddiameter (smaller than the first diameter), and actuation members sizedto approximately the same second diameter. Sliding sleeve members withineach family can have different lengths of protrusions, and actuationmembers within each family can have different lengths of grooves.Sliding sleeve members belonging to the second family can be locateddownhole from sliding sleeve members belonging to the first family.Actuation members belonging to the second family can then traveldownhole past all sliding sleeve members belonging to the first family,even if the grooves of these actuation members are the same length orlonger than the protrusions of one or more sliding sleeve members of thefirst family. The ability of the actuation members in the second familyto avoid capture by sliding sleeve members of the first family is due tothe mismatch in diameters.

The use of multiple families can allow further diversity in the slidingsleeve members, so that the stage count within the wellbore (i.e. thenumber of sliding sleeve members and ports) be increased.

Embodiments of the present invention provide for a multi-stage hydraulicfracturing completions system that allows for sequential and/orstaggered (e.g. leapfrogged) treatment of wellbore intervals. This maybe achieved while avoiding obstruction of productive length of thewellbore with actuation members, plugs or balls after the treatments ateach stage are completed. Embodiments of the present invention mayachieve this while also maintaining a substantially unencumberedproduction pathway. This may be facilitated by the controllable releaseof actuation members from mated sliding sleeve members.

Embodiments of the present invention can provide for the automaticrelease of actuation members in the event of a screenout event, to clearthe proppant from the wellbore and move completion operations to thenext stage without the need for coiled tubing, wireline or perforatingguns to perforate the well casing to regain reservoir injectivity. Thisreleasing action will open up the wellbore below the (now released)actuation member to hydraulic pressure from surface, thus allowingpumping operations to continue. This can allow the treatment fluids tocontinue to be injected into the intervals below the screened out zone.

Embodiments of the present invention can also allow for the release ofactuation members in the event of an interval of the reservoir beingunable to accept treatment fluid at a desirable rate. This can againfacilitate continuation of the completion operations without the needfor coiled tubing, wireline or perforating guns to perforate the wellcasing and establish a new injectivity point to the reservoir.

Embodiments of the present invention can be applied for screenoutremediation or untreatable sections of a reservoir.

Embodiments of the present invention aim to increase efficiency ofmultistage hydraulic fracturing operations by providing a method foractuation members (plugs) in actuation member-activated sliding sleevesystems to be released from their mated sliding sleeves after fracturingplacement at the corresponding interval is complete. A releasedactuation member can then be displaced to a lower portion of thewellbore (e.g. a storage rathole) where it will remain, and where itwill not interfere with further operations.

Embodiments of the present invention may be used to purposefully createscreenout events. Some reservoirs are observed to have better productionwhen they are screened out.

Embodiments of the present invention may be employed to provide a methodof leapfrog fracturing, also known as staggered fracturing. Leapfrogfracturing is a method of non-sequential fracturing that is believed toincrease the productivity from fracture treatments in certain type ofreservoirs. Leapfrog fracturing can be described as a method in which alowermost stage is fractured, a stage more shallow then the nextshallowest stage is fractured and then one or more stages between thesetwo fractured stages are fractured. Embodiments of the present inventionprovide a method and system for leapfrog fracturing without the use ofcoiled tubing and which may potentially be performed as efficiently asother current fracturing methods. In one embodiment, leapfrog fracturingcomprises fracturing the well in the following sequence; deepest stage,third deepest stage, second deepest stage, fourth deepest stage, sixthdeepest stage, fifth deepest stage, etc.

In some embodiments, in the leapfrog fracturing, an actuation member canbe used to uncover a first one of a plurality of ports by interoperatingwith a corresponding first sliding sleeve member. The actuation membercan then be released from the first sliding sleeve member as describedabove and moved downhole. The same actuation member or a differentactuation member can then be used to uncover a second one of a pluralityof ports by interoperating with a corresponding second sliding sleevemember. This second port is non-adjacent to the first port, in the sensethat one or more further ports are located along the borehole betweenthe first port and the second port. These further ports can besubsequently uncovered, or previously uncovered.

In the following paragraphs, embodiments will be described in detail byway of example with reference to the accompanying drawings, which arenot drawn to scale, and the illustrated components are not necessarilydrawn proportionately to one another. Throughout this description, theembodiments and examples shown should be considered as exemplars, ratherthan as limitations of the present disclosure.

FIG. 1 illustrates a wellbore 110 and a casing 112 (not showing thestopping member and the release mechanism) included in the wellbore, andhaving a plurality of ports 114 located along the length of the casing.An actuation member 116 according to the present invention is piecedwithin a borehole 118 which is defined by the inner sidewalls of thecasing, and travels (under hydraulic pressure) through the borehole inthe downhole direction. Multiple sliding sleeve members 120 according tothe present invention are shown which initially cover the various ports114. The sliding sleeve members include protrusions 122 of varyinglengths, and the actuation member 116 includes a groove 124 (radialkeyway) of a given length. The actuation member 116 travels down theborehole until it reaches a sliding sleeve member 120 having protrusions122 which are equal to or shorter in (longitudinal) length than thecorresponding groove in the actuation member. At this point theprotrusions matingly fit within the groove 124 of the actuation member116, This mating allows downhole force to be applied to the slidingsleeve member in order to move it downhole, thereby uncovering theassociated ports.

Alternatively, the grooves may be disposed on the sliding sleeve membersand the corresponding protrusions may be disposed on the actuationmembers. Other keyed systems which allow for actuation members toselectively engage with particular sliding sleeve members may also beemployed.

The casing can be viewed as a structure within the wellbore which isrelatively impermeable to hydraulic fracking fluid. The casing can beformed of one or more mating sections of selected materials.

FIGS. 2A, 2B and 2C illustrate, in cross-sectional view, embodiments ofactuation member 200 a/b/c (before being placed in the casing), and FIG.3 illustrates a part of a casing 370 and a sliding sleeve member 340,provided in accordance with an embodiment of the present invention. Theactuation member 200 a/b/c, the casing 370 and the sliding sleeve member340 are typically of generally cylindrical shape and are located, inoperation, within a wellbore. One or more ports are located at variouslocations along the length of the casing, which provide for fluidiccommunication between the borehole defined by the casing and thesidewalls of the wellbore. The fluidic communication via an exposed portfacilitates hydraulic fracturing operations, in which fracking fluid ispumped downhole through the borehole and out of the exposed ports. Eachof the sliding sleeve members is placed within the borehole andinitially covers one or more of the ports and is movable, using a matingactuation member, so as to selectably uncover these ports. The actuationmember is configured for travelling down the borehole in a longitudinaldirection and has an uphole end portion 202 a/b/c and a downhole portion204 a/b/c.

The outer face of the actuation member 200 a/b/c includes a wedgedportion 220 a/b/c towards downhole end portion 204 a/b/c. The wedgedportion 220 a/b/c can be frusto-conical in shape. A groove 225 a/b/c isformed at least partially circumferentially around an outer face of theactuation member 200 a/b/c. The groove has a first length 227 a/b/c inthe longitudinal direction 201. The groove 225 a/b/c includes a radiallyoriented face 229 a/b/c which is located at the uphole end of thegroove. The face 229 a/b/c may be, but is not necessarily radiallyoriented at right angles to the longitudinal direction 201. The face 229a/b may be oriented at an acute angle to the longitudinal direction 201(that is, toward the downhole and in the direction of travel of theactuation member). The acute angle can be an 89 degree angle, an 85degree angle, or another angle, e.g. smaller than 89 degrees, or between85 degrees and 90 degrees. In another embodiment, the acute angle can be50 degrees, or 45 to 55 degrees, or another angle, e.g. between 40 and90 degrees. The angle and size of the face 229 a/b/c is selected sothat, upon engagement with a protrusion of the sliding sleeve member 340(as described below), the protrusion will remain engaged in the groove225 a/b/c (and with the face 229 a/b/c). The protrusion 359 of thecorresponding sliding sleeve has a similarly sized and angled matingface.

The configuration of the actuation member for travelling down theborehole in a longitudinal direction includes sizing and shaping theactuation member to closely match the borehole of the casing (such asthe actuation member of FIG. 2A). Some variation in diameter may beallowed in the case that different families of actuation members areprovided.

Alternatively the configuration of the actuation member includesproviding an actuation member with a longitudinal aperture 215 extendingfrom an uphole face of the actuation member to a downhole face of theactuation member, and a plug member seat 110 within the longitudinalaperture, and placing of a plug member 205 (such as a ball) into a theplug member seat 210. The plug member 205 blocks a longitudinal aperture215 of the actuator member which, when unblocked, allows fluidiccommunication between an uphole end 102 of the actuation member and adownhole end 204 of the actuation member (for example actuation membersof FIGS. 2B and 2C).

Hydraulic fluid is applied under pressure uphole of the actuationmember. Due to its slidability within the borehole and its size, shapeand/or blocked longitudinal aperture, the actuation member is motivatedto move downhole under the hydraulic fluid pressure. In someembodiments, the plug member is dissolvable or otherwise removable. Thisprovides the capability to unblock the borehole after the actuationmember has engaged with and operated a sliding sleeve member to open aport in the borehole sidewall.

In some embodiments the wedged portion is provided along a leading edgeof the actuation member proximate to the downhole end (FIG. 2c ). Thewedged portion can be frustro-conical in shape and, in the embodimentillustrated in FIG. 4c , extends from the outer edge of the aperture 215c to a largest outer diameter of the actuation member.

As depicted in FIG. 3, the sliding sleeve member 340 includes anaperture 342 for receiving the actuation member therein. For example,the sliding sleeve member can be generally shaped as a hollow cylinder.The aperture has a diameter which is approximately the same orincrementally larger than the overall largest diameter of the actuationmember, such as 200 a, 200 b or 200 c, so that the actuation member canenter and potentially pass through the aperture 242.

The sliding sleeve member 340 initially covers a port 345 in theborehole. The port can extend partially or fully around thecircumference of the casing, and multiple such ports may be provided.The sliding sleeve member 340 can be fixed in place using shear pins 350or another frangible or disengagable securing member. Once the shearpins 350 have been broken due to application of force in thelongitudinal direction, the sliding sleeve member 340 is slidable withinthe borehole. As such, the sliding sleeve member 340 is configured, uponapplication of force in the longitudinal direction 301, to move downholein the longitudinal direction, thereby uncovering the port 345. Theshear pins may be rated to break under application of a rated amount offorce, and hence the sliding sleeve member may be configured to moveonly in response to a predetermined amount of force which is at leastthe rated amount of force.

In some embodiments, a seal may be provided between the sliding sleevemember 340 and the casing 370. The seal is configured to seal/isolatethe port 345 when the sliding sleeve member is in the closed position.

The sliding sleeve member 340 includes a deformation region and one ormore inward-facing protrusions 355 connected to the sliding sleevemember in the deformation region. The protrusions 355 are biased toprotrude radially into the aperture 342 so as to contact the wedgedportion 320 during travel of the actuation member 200 past theprotrusions 355. The protrusions 355 are movable radially outward by thewedged portion 320 of the actuation member 200 when the actuation membermoves downhole past the protrusions 355.

In the presently illustrated embodiment, the deformation region of thesliding sleeve member 340 is defined by longitudinal extensions 360extending towards downhole, wherein the protrusions 355 are located ator near ends of longitudinal extensions 360. The extensions 360 may beviewed as cantilever springs upon which the protrusions 355 are mounted.The cantilever springs are formed of a resilient material, such asmetal, which applies inward biasing force to the protrusions in responseto being pushed outward by the wedged portion 320 of the actuatingmember 200. The cantilever springs can refer to elongated, resilientlyflexible bodies anchored at one end. It is noted that the boreholeincludes a cavity 365 which surrounds a portion of the sliding sleevemember in the vicinity of the protrusions 355. This cavity 365 providesspace for outward motion of the protrusions 355 (and portions of theextensions 360). The extensions 360 can be formed by creatinglongitudinal cuts 357 in the cylindrical body of the sliding sleevemember 340, the cuts extending to a downhole edge 359 of the cylindricalbody. The cuts also extend through an inwardly-projecting (full orpartial) annulus from which the protrusions 355 are formed. Strainrelief 358 can also be included to facilitate flexing of the extensions360 as cantilever springs.

Alternative structures for holding and inwardly biasing the protrusions355 can also be used. For example, the cuts 357 are not necessarilylongitudinal and do not necessarily extend to the downhole edge 359. Thecuts pass through a deformation region of the sliding sleeve member, thedeformation region including the inward-facing protrusions 355 formed onan interior face of the sliding sleeve member hollow tube. Resilientmaterial (e.g. spring steel) in the deformation region provides inwardbias to the protrusions, and the cuts allow radial outward movement ofthe protrusions due to the wedged portion 320. Again, the boreholeincludes the cavity 365 to allow the radial outward movement of theprotrusions. In another embodiment, the protrusions are movably housedin a cartridge placed in a hole of the sliding sleeve. The protrusionsmove radially, and are biased inwardly for example using coil springs,hydraulic fluid or another mechanism.

The protrusions 355 have a second length 356 in the longitudinaldirection 301. In the presently illustrated case, the second length isless than or equal to the first length 327 of the groove 325 in theactuation member 200. As such, the protrusions 355 are configured, uponalignment with the groove 325 of the actuation member, to move radiallyinward due to the biasing force applied on the protrusions (the biasingforce being generated in response to deformation of the resilientdeformation region by travel of the wedged portion of the actuationmember). Upon such radial inward motion, the protrusions 355 arereceived within the groove 325 of the actuation member 200. Theprotrusions and the groove are configured so that, once received, theprotrusions are retained within the groove substantially withoutslippage that would cause the protrusions to fall out of the groove.This action is referred to as a keying action, in which only actuationmembers having a sufficiently long groove allow for protrusions of agiven (same or shorter) length to be received in the groove.

Upon retention of the protrusions 355 within the groove 325, theradially oriented face 329 of the groove matingly engages respectiveradially oriented faces 359 of each of the protrusions 355. Thisengagement allows a transfer of the predetermined amount of force(required to slide the sliding sleeve) from the actuation member to thesleeve member. In more detail, hydraulic pressure imparts thepredetermined amount of force onto the actuation member, the force istransferred via the mating faces 329, 359 onto the protrusions, and, byvirtue of connection of the protrusions with the sliding sleeve member340, the force causes shearing of the shear pins 350 and sliding of thesliding sleeve member. In some embodiments, the predetermined amount offorce is at least equal to the rated shearing force of the shear pins.

It is noted that, if the second length 356 of the protrusions weregreater than the first length 327 of the groove, then the protrusionswould be too long to fit within the groove. In this case, the actuationmember would pass through the sliding sleeve without the protrusionsbeing received in the groove. This feature can be used to selectablypass the actuation member through other sliding sleeve members (havingprotrusions which are longer than the first length 327), upstream of theillustrated sliding sleeve member. This feature can also be used toselectably pass another actuation member (having a groove which isshorter than the second length 356) through the illustrated slidingsleeve member, and toward other sliding sleeve members downstream of theillustrated sliding sleeve member. A plurality of sliding sleeve membersand actuation members can be provided and used within the borehole, inwhich different sliding sleeve members have differently-lengthedprotrusions, and different actuation members have differently-lengthedgrooves.

The inner diameter of the wedged portion may be smaller than thediameter defined by the inner edges of the protrusions 355, so as toreduce shock when the wedged portion contacts the protrusions.

The depth of the groove is generally sufficient for holding at leastpart of the protrusions 355 without slippage, over-stressing of thesprings, etc.

In some embodiments, rather than or in addition to providing a resilientdeformation region of the sliding sleeve member (which allows theprotrusions on the sliding sleeve member to be pushed outward by thewedged portion of the actuation member), the actuation member itself canbe resiliently deformable in the radial inward direction. A portion ofthe actuation member which is resiliently deformable may also bereferred to as a (resilient) deformation region. In some embodiments,the deformation region of the actuation member is the trailing portionof the actuation member. The deformation region of the actuation membermay be colleted and includes the actuation member groove. Longitudinalcuts (collets) can be formed within a resilient material forming the(hollow) actuation member in order to allow the actuation member to beradially inwardly compressible in response to force imparted on thewedged portion by the protrusions (of the sliding sleeve member) whenthe actuation member moves downhole past the protrusions. It is notedthat a variety of design options are available in which: a portion ofthe sliding sleeve member radially outwardly deforms while the actuationmember remains undeformed; the actuation member radially inwardlydeforms while the sliding sleeve member remains undeformed; or both theportion of the sliding sleeve member radially outwardly deforms and theactuation member radially inwardly deforms.

FIGS. 4A and 4B illustrate, in cross-section, an exemplary releasemechanism 410 in the form of a wedge-shaped body engaging with anexemplary actuation member 420 (having groove(s)) to cause the actuationmember to disengage from an exemplary sliding sleeve member 430 (havingprotrusion(s)) after the actuation member 420 has received the slidingsleeve member's protrusions 436 within the actuation member's grooves426, and after the actuation member has moved the sliding sleeve memberdownhole. FIG. 4D shows the sliding sleeve member having moved downholefrom its position in FIG. 4C, thus uncovering the port. When the slidingsleeve member 430 moves toward its open position, the actuation member420, correspondingly moves downhole, thus encountering the wedge-shapedbody 410 protruding inward into the borehole. The wedge-shaped body 410of the release mechanism is tapered toward (i.e. narrows in) thedownhole direction. In some embodiments, the wedge-shaped body 410 canbe an annulus with an inner surface which is tapered toward the downholedirection. In some embodiments, one or more portions of the annulus canbe omitted. The release mechanism can alternatively be non-tapered andnon-wedge-shaped. For example the release mechanism can protruderadially inward with an uphole face that is perpendicular to thedownhole direction.

As the actuation member 420 moves downhole, the wedge-shaped body 410interferes with the wedged portion 422 of the actuation member, asdescribed elsewhere herein. The wedged portion 422 is integrated with aninwardly deformable portion 424 of the actuation member 410. As thedeformable portion of the actuation member 420 is more deformable thanthe wedge-shaped body 410, this part of the actuation member is deformedradially inward as the actuation member moves downhole, as shown in FIG.4D. The grooves 426 of the actuation member 420 are also mounted on theinwardly deformable portion 424 and consequently are pushed radiallyinward. This causes the grooves 426 to disengage from the protrusions436 of the sliding sleeve member. The consequence of this deformation isthat the actuation member 420 releases from the sliding sleeve member430 and is then able to travel downhole where it may potentiallyencounter other mating and/or non-mating sliding sleeve members. Assuch, a levering action is performed which releases the actuationmember. The consequence of the levering action, radially inwarddeformation of the actuation member and its release is shown in FIG. 4E

FIGS. 5A to 5J illustrate operation of a system comprising a stoppingmember along with the release mechanism. In FIG. 5A, the sliding sleevemember 530 initially covers the ports 516. In FIG. 5B, the actuationmember enters the aperture of the sliding sleeve member and approachesthe protrusions 536 under a first predetermined amount offorce/pressure. In FIG. 5C, the protrusions 536 of the sliding sleevemember have engaged the groove 526 of the actuation member, theprotrusions having been pressed into the groove due to the biasingforce. In FIG. 5D, the locked actuation member and the sliding sleevehas moved further downhole to the opening position thereby opening theports 516, and leading edge 514 of sleeve resting on the stoppingmember(s) 512, 518. The stopping members inhibit (at least initially)further downhole motion of the sliding sleeve member and actuationmember locked thereto. This keeps the wedged portion of the actuationmember from contacting the release mechanism 510.

In FIGS. 5E and 5F balls have been used to block the opened ports 516,which results in or otherwise facilitates increasing the pressure to asecond predetermined amount, which would disengage the stopping member514. In more detail, because the ports are blocked, hydraulic pressureon the actuation member increases, or is easier to increase becausehydraulic fluid can no longer exit the ports. This increased pressure onthe actuation member causes increased force on the stopping member,which is designed to break or otherwise disengage under a predeterminedforce, such as the increased force. As already mentioned, the stoppingmember can be a shear pin or shear ring.

FIGS. 5G and 5H show disengagement of the stopping member to allowfurther downhole movement of the actuation member and its interactionwith the release mechanism 510, to release the actuation member 520 fromthe sliding sleeve member 530. (The release of the actuation member isvia the mechanism or levering action as discussed further, for examplewith respect to FIGS. 4A and 4B.) The actuation member is then able totravel downhole where it may potentially encounter other mating and/ornon-mating sliding sleeve members, and eventually be expelled out of thesystem or held in an end reservoir of the borehole. The releasemechanism can be unanchored and also travel downhole, or anchored on atrack, tether, etc.

FIGS. 6A to 6I illustrate operation of a system comprising a stoppingmember along with the release mechanism same as described in FIGS. 5a to5J, with the difference that in this embodiment, interval screenoutevent(s) provide the increase in pressure for disengagement of thestopping member. The screenout event is shown in FIG. 6E, where a “T”shaped body blocking the ports represents a screenout event, for examplein which granular material has clogged the ports. The screenout eventsmay be intentional or unintentional.

FIGS. 7A to 7H illustrate operation of a system comprising a stoppingmember along with the release mechanism same as described in FIGS. 5A to5J, with the difference that in this embodiment, failure of port(s) toaccept hydraulic fluid provides the increase in pressure fordisengagement of the stopping member. Although the ports are shown asunblocked, hydraulic fluid is inhibited from exiting via the ports, orcan only exit to a limited amount. Automatic release under suchcircumstances can be beneficial in moving the fracturing operationsonward to a further stage.

FIGS. 8A to 8I illustrate a non-sequential (leap frog) fracking systemoperation. In FIG. 8A, an actuation member 860 begins travellingdownhole, and all sliding sleeve members 815, 825, 835, 845 are in theclosed (port-covering) position. In FIG. 8B, the actuation member 860has engaged with the sliding sleeve member 835, and moved the slidingsleeve member 835 to the open position, wherein ports 836 are opened,and a leading edge of the sleeve member 835 is resting on the stoppingmember 832. In FIG. 8C “drop balls” 862 being travelling downhole toclose the opened ports and to increase the pressure in the system. InFIG. 8D, the ports 836 have been closed with the balls 862 and theactuation member has been disengaged due to shearing of the stoppingmember 832 by increased pressure, and the action of the releasemechanism 830, and is now engaged with the sliding sleeve member 845. InFIG. 8D, the actuation member 860 has moved the sliding sleeve member845 to the open position, thereby opening ports 846, and a secondactuation member 864 begins travelling downhole.

In FIG. 8E the second actuation member 864 is travelling furtherdownhole towards sliding sleeve 825, after engaging and moving thesliding sleeve 815 to open position and opening ports 816 for fracking,when the leading edge of the sliding sleeve was engaged with thestopping member 812 under a predetermined pressure, and now beingreleased due to increase in pressure achieved by closing the ports 816with drop balls 866.

In FIG. 8F the second actuation member 864 has engaged with the slidingsleeve member 825, and moved the sliding sleeve member 825 to the openposition, wherein ports 826 are opened, and a leading edge of the sleevemember 835 is resting on the stopping member 822 under anotherpredetermined pressure conditions.

In FIG. 8G “drop balls” 868 travelling downhole to close the openedports 826 and to increase the pressure in the system to anotherpredetermined level.

In FIG. 8H, the ports 826 have been closed with the balls 868 and theactuation member 864 has been disengaged due to shearing of the stoppingmember 822 by increased pressure, and the action of the releasemechanism 820, and is now being expelled from the system.

In FIG. 8I the various drop balls have been cleared from the system.

As such two actuation members have been used to achieve non-sequentialopening of ports.

FIGS. 9A to 9C illustrate alternative embodiments wherein the actuationmember can be configured to hold a plug member 905 (such as a ball) intoa corresponding (e.g. tapered) plug member seat 910 of the actuationmember. The plug member 905 blocks a longitudinal aperture 915 of theactuator member which, when unblocked, allows fluidic communicationbetween an uphole end 902 of the actuation member and a downhole end 904of the actuation member.

As used herein, the “present disclosure” or “present invention” refersto any one of the embodiments described herein, and any equivalents.Furthermore, reference to various aspects of the invention throughoutthis document does not mean that all claimed embodiments or methods mustinclude the referenced aspects or features.

It should be understood that any of the foregoing configurations andspecialized components or may be interchangeably used with any of theapparatus or systems of the preceding embodiments. Although illustrativeembodiments are described hereinabove, it will be evident to one skilledin the art that various changes and modifications may be made thereinwithout departing from the scope of the disclosure. It is intended inthe appended claims to cover all such changes and modifications thatfall within the true spirit and scope of the disclosure.

Although embodiments of the invention have been described above, it isnot limited thereto and it will be apparent to those skilled in the artthat numerous modifications form part of the present invention insofaras they do not depart from the spirit, nature and scope of the claimedand described invention.

We claim:
 1. A system for controllably exposing selected locations alonga wellbore to a pressurized fluid, the wellbore including an elongatedcasing disposed therein, the casing defining an internal boreholeextending longitudinally with the wellbore, the casing having one ormore ports extending through the casing, the system comprising: anactuation member configured for travelling down the borehole in alongitudinal direction; a first sliding sleeve member for disposalwithin the borehole and having an aperture for receiving the actuationmember therein, the first sliding sleeve member configured to initiallycover one of the one or more ports, and further configured to movedownhole in response to a predetermined amount of force in thelongitudinal direction to uncover the port; wherein the actuation membercomprises a first engagement portion configured to matingly engage witha corresponding second engagement portion of the first sliding sleevemember to allow for the predetermined amount of force to be transferredfrom the actuation member to the first sliding sleeve member; and astopping member affixed to the casing downhole of the first slidingsleeve member, the stopping member configured to contact the firstsliding sleeve member after the first sliding sleeve member has moved afirst distance downhole and initially inhibit further downhole travel ofthe first sliding sleeve member, the stopping member configured torelease under a second predetermined amount of force to allow saidfurther downhole travel of the first sliding sleeve member; wherein thefirst engagement portion and the second engagement portion areconfigured to release from one another upon said further downhole travelof the first sliding sleeve member under said second predeterminedamount of force, to cause the actuation member to disengage from thefirst sliding sleeve member.
 2. The system of claim 1, wherein the firstengagement portion of the actuation member comprises a wedged portionand a groove formed at least partially circumferentially around an outersurface of the actuation member, and the first engagement portion of thefirst sliding sleeve member comprises one or more inward-facingprotrusions connected to the first sliding sleeve member, and protrudingradially into the aperture, one or both of the protrusions and thegroove configured, upon alignment of the protrusions and the groove, tomove radially toward the other due to a biasing force so that theprotrusions are received within the groove, whereupon the predeterminedamount of force is transferred from the actuation member to the firstsliding sleeve member.
 3. The system of claim 2, wherein one or both ofthe actuation member and the first sliding sleeve member have adeformation region.
 4. The system of claim 2, wherein the actuationmember has a deformation region comprising the groove disposed thereon;wherein the biasing force is generated by resilient radial inwarddeformation of the deformation region, said resilient radial inwarddeformation occurring in response to action of the wedged portion on theinward-facing protrusions during downhole motion of the actuation memberpast the inward-facing protrusions.
 5. The system of claim 3, whereindownhole of the stopping member, the borehole or casing has a narrowingportion configured to contact and apply force on the wedged portion ofthe actuation member due to said further downhole travel, said forcecausing a second instance of radial inward deformation of thedeformation region to release the inward-facing protrusions from thegroove, to cause the actuation member to disengage from the firstsliding sleeve member.
 6. The system of claim 3, wherein downhole of thestopping member the casing comprises a wedge-shaped body configured tocontact to and apply force on the wedged portion of the actuation memberdue to said further downhole travel, said force causing a secondinstance of radial inward deformation of the deformation region torelease the inward-facing protrusions from the groove, to cause theactuation member to disengage from the first sliding sleeve member. 7.The system claim 1, further comprising: a second sliding sleeve memberfor disposal within the borehole uphole of the first sliding sleevemember, the second sliding sleeve member having a second aperture forreceiving the actuation member therein, the second sliding sleeve memberinitially covering a second port of the one or more ports extendingthrough the casing and configured, upon application of a secondpredetermined amount of force applied in the longitudinal direction, tomove downhole in the longitudinal direction, thereby uncovering thesecond port; a second stopping member affixed to the casing downhole ofthe second sliding sleeve member, the second stopping member configuredto contact the second sliding sleeve member after the second slidingsleeve member has moved a first distance downhole and initially inhibitfurther downhole travel of the second sliding sleeve member, the secondstopping member configured to release under another predetermined amountof force to allow said further downhole travel of the second slidingsleeve member; wherein the second sliding sleeve member comprises anengagement portion configured to matingly engage the first engagementportion of the actuation member, to allow for the predetermined amountof force to be transferred from the actuation member to the secondsliding sleeve member; wherein the first engagement portion and theengagement portion of the second sliding sleeve member are configured torelease from one another upon said further downhole travel of the secondsliding sleeve member under said second predetermined amount of force,to cause the actuation member to disengage from the second slidingsleeve member.
 8. The system of claim 2, wherein the wedged portion islocated along a leading edge of the actuation member.
 9. The system ofclaim 2, wherein the wedged portion protrudes from the outer surface ofthe actuation member at a location between a leading edge and a trailingedge of the actuation member.
 10. The system of claim 1, wherein theactuation member the actuation member initially substantially fills theborehole and travels down the borehole in response to hydraulic pressureapplied uphole of the actuation member.
 11. The system of claim 1,wherein the actuation member includes a longitudinal aperture extendingfrom an uphole face of the actuation member to a downhole face of theactuation member, and a plug member seat within the longitudinalaperture, the plug member seat configured for receiving and retaining aplug member for blocking the longitudinal aperture.
 12. The system ofclaim 11, wherein the plug member is controllably dissolvable.
 13. Thesystem of claim 2, wherein the actuation member includes a leadingportion and a trailing portion, the leading portion located downhole ofthe trailing portion, and wherein the trailing portion is compressibleradially inwardly due to force applied by the one or more inward-facingprotrusions on the wedged portion when the actuation member movesdownhole past the one or more inward-facing protrusions.
 14. The systemof claim 13, wherein the trailing portion comprises resilientlydeformable collets actuated for radially inward compression.
 15. Asystem for controllably exposing selected locations along a wellbore toa pressurized fluid, the wellbore including an elongated casing disposedtherein, the casing defining an internal borehole extendinglongitudinally with the wellbore, the casing having one or more portsextending through the casing, the system comprising: an actuation memberconfigured for travelling down the borehole in a longitudinal direction;at least one sliding sleeve member for disposal within the borehole andeach having an aperture for receiving the actuation member therein, theat least one sliding sleeve member configured to initially cover arespective port, and further configured to move downhole in response toa predetermined amount of force in the longitudinal direction to uncoverthe port; wherein the actuation member comprises a first engagementportion configured to matingly engage with a corresponding secondengagement portion of the at least one sliding sleeve member to allowfor the predetermined amount of force to be transferred from theactuation member to the at least one sliding sleeve member; a stoppingmember affixed to the casing downhole of one or more of the at least onesliding sleeve member, the stopping member configured to contact the atleast one sliding sleeve member after the at least one sliding sleevemember has moved a first distance downhole and initially inhibit furtherdownhole travel of the at least one sliding sleeve member, the stoppingmember configured to release under a second predetermined amount offorce to allow said further downhole travel of the at least one slidingsleeve member; wherein the first engagement portion and the secondengagement portion are configured to release from one another upon saidfurther downhole travel of the at least one sliding sleeve member undersaid second predetermined amount of force, to cause the actuation memberto disengage from the at least one sliding sleeve member.
 16. The systemof claim 15, wherein the stopping member is affixed to the casingdownhole of each of the at least one sliding sleeve member.